An unusually high South Shore swell kept boat harbors on alert from Wai'anae to Ala Moana yesterday and two lifeguard teams at Waikiki and Ala Moana bouncing across the waves on rescue craft.

It was a surfboard-breaking, leash-snapping day in which lifeguards rescued more than 100 swimmers and assisted 200 surfers back to shore before the sun went down at world-famous Waikiki Beach.

"It's been nonstop since we jumped in the water today," said lifeguard Garvin Freitas, who said he'd lost count of the dozens of surfers he and his partner, Ramsey Rosa, had dragged in by midday.

"This is very unusual. I didn't expect it to be this big."

Freitas said about half the rescues were tourists "in over their heads" and the other half were locals who misjudged the intensity of the waves. Waikiki's waves yesterday had faces of up to 15 feet, making the North Shore's tame 6-footers seem, for once, puny by comparison.

Even as exhausted surfers were being plucked from the waves two and three at a time, lifeguards shifted gears to rescue eight divers from the waters off Magic Island.

"They kept getting swept out to sea and into the impact zone," said lifeguard and South Shore operations officer Capt. Paul Merino. "So, we had to pull them all out."

Merino said part of the problem has been surfboard rental stands that hawk boards to visitors who have no business going out on days like yesterday.

But Stanton Vierra, 20, afternoon manager of Hawai'i Oceans Waikiki surfboard stand, said he had warned customers about yesterday's surfing conditions, and even refused to rent boards to those who were obviously beginners.

"Just be careful," he told Chris Wood of Brisbane, Australia, who rented a board along with three friends. "If you feel like you need to, wave to the lifeguards on the Jet Skis and they'll come get you."

Vierra, who has surfed Waikiki Beach his whole life, said he had gone out himself earlier in the day, "and it just got bigger and bigger."

Meanwhile, there were reports of the high surf throwing sand across Farrington Highway at Makaha, and, according to the National Weather Service, ocean waters splashed over the highway at Nanakuli.

State Department of Land and Natural Resources spokeswoman Deborah Ward said the Ala Wai Boat Harbor as well as the Ke'ehi Lagoon and Wai'anae small boat harbors reported calm waters inside the harbors, but rough seas outside.

William Aila, harbor master at Wai'anae, said the intense south swell combined with an early winter swell from the northwest was a concern for boaters leaving and entering the harbor. Aila posted a black flag to warn boaters to only make the attempt between wave sets.

Back in Waikiki, lifeguard Jerry Balaker, manning the 2B tower near the landmark statue of Duke Kahanamoku, watched a rescue craft tote in one dazed tourist only to take off to haul in more.

"He's OK," said Balaker as the visitor stumbled toward the shore. "He might have just been a little out of his element."

Within three minutes two rescue craft appeared with a total of four surfers, who thanked the lifeguards, shook their hands, and then staggered toward the shore.

"Most of them are grateful," said Balaker.

Ai Kimura, 21, of Nara, Japan, and her friend, Masakazu Kono, 23, were among the grateful surfers brought in.

"We swam too far away," said a sheepish Kimura. "And the waves and the current were much more than we thought."

Moments later seasoned surfer Jason Devlin of Las Vegas called it quits for the day.

"I've come here often and I've never seen anything like this," said Devlin, elated but beat. "The surf's about three times higher than I've ever seen it before. I only caught four waves today.

"I'm lucky I didn't get squashed. I felt like an ant out there a couple of times."

He said he had lost track of his father, James Devlin, with whom he had been surfing. The elder Devlin showed up a short time later, pooped and unwilling to comment on having had his leash snapped by the current.

"He's surfed this beach many times," said the younger Devlin. "But he said, 'I don't want to be famous for drowning out there today.'"

Reach Will Hoover at whoover@honoluluadvertiser.com.